Apparatus for insulating electrical resistor elements



g- 29, 1933- V E. LTWIEGAND ET-AL 1,924,474

APPARATUS FOR INSULATING ELECTRICAL RESISTOR ELEMENTS Filed Feb. 15, 1950 6 Sheets-Sheet 1 g- 29, 1933- V E. L. WIEGAND ET AL 1,924,474

APPARATUS FOR INSULATING ELECTRICAL RESISTOR ELEMENTS Filed Feb. 15, 1930 e Shets-Sheet 2 I 3/ 3/ 3.9 i l 1 33 l 3% i fi 1 1 7 2 53 I 20 3a I -42 I 5 5 2#' '1 Z5/ 29 49 z 5 26 v a, 2/ 24 a] j: j- I E 3 23 22 I As 5 1 /6 2/ a l o 20 o O I I Q I i W x. W M J7} W WW W6 w WA 7 dbto'amq Aug. 29, 1933- E. WIEGAND ET AL APPARATUS FOR INSULATING ELECTRICAL RESISTOR ELEMENTS Filed Feb. 15, 1930 6 Sheets-Sheet s Aug; 29, 1933. 1,924,474

APPARATUS FOR INSULATING ELECTRICAL RESISTOR ELEMENTS E. L. WIEGAND El AL Filed Feb. 15, 1950 6 Sheets-Sheet 4 u 29, 1933. y E. L.- WI EC iAND ET AL 1,924,474

APPARATUS FOR INSULATING ELECTRICAL RESISTOR ELEMENTS 1 Filed F eb. 15, 19:50 6 Sheets-Sheet 5 .1933- E. L. WIE GAN D ET AL 1,924,474

I I ELEMENTS APPARATUS FOR INSULATING ELECTRICAL RESISTOR Sheets-Sheet .6

Filed Feb. 15, 19:50

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Patented Aug. 29, 1933 I UNITED STATES PATENT OFFICE APPARATUS FOR INSULATING ELECTRICAL imsisroa ELEMENTS I Edwin L. Wiegand and Albert P. Wiegamh Pittsburgh, Pa.

This invention relates to an apparatus for insulating electrical resistors.

One of the main objects of the invention is to provide an apparatus which is well adapted for insulating electrical resistors of the character described and which is chiefly characterized by its adaptability for extruding the insulating material or insulation forming material about a resistor thus forming a resistor element in which the material surrounding-the resistor is highly refractory, dense and impervious to air and outside agents and also comparatively infusible.

Another object of 'the invention is to provide an apparatus of the character described which is eiiicient and dependable in operation and comprises comparatively few parts.

A further object of the invention is to provide an apparatus for forming electrical resistors which consists essentially of an extrusion device adapted to extrude a material about a resistor.

- Another object of the invention is to provide an apparatus of the character described which is welladapted for insulating electrical resistors of different shapes and sizes which may be either straight or convoluted, hollow or solid and sheathed or unsheathed.

A further object of the invention is to provide an apparatus, for insulating electrical resistors which is capable of forming a resistor element which will withstand a maximum amount of energy input per cubic inch of element displacement without injury to itself.

Another object of the invention is to provide an apparatus of thecharacter described which em-.

bodies a mold into which may be inserted the sheath for enclosing the unit, and means for extruding an insulation forming material into the mold and about the resistor under pressure.

A still further object of the invention. is to provide an apparatus'of the character described which is provided with means for positioning a form or core on whicharesistor is secured. and means for extruding insulation forming material about the form or core and around the resistor thus forming a resistor unit in a single operation.

' Heretofore, electrical heating units of the general character herein referred to have been formed by supporting a resistor on a suitable form or core or in a sheath and then compacting comparatively dry material around the resistor or pouring a semi-fluid material for insulating the resistor. These methods while very tedious, are satisfactory'for certain types of heating units; but where a heating unit is desired which will produce a great amount of heat in a short timaor where a heating-unit is desired which will occupy a very litle space and yet produce a great amount of heat, the apparatus herein described has, because of its efficacy in effectively insulating a highly condensed resistor, been found mostsatisfactory and efficient. With theapparatus herein described, we are able to produce a heating unit which will rate as high as 250 watts per cubic inch of element displacement. Moreover, the re.- fractory material is more penetrative, homogeneous and compact and for this reason the 'coils or convolutions of the resistor may be positioned closer together than has heretofore been possible. The apparatus herein disclosed also enables us to reducematerially the number of operations necessary for forming the heating unit, and is therefore well adapted for the quantity production of heating units of uniform quality and at comparatively low cost. Moreover, the apparatus is relatively inexpensive and consists of comparatively few parts and may be made semi-automatic in operation thus reducing materially the manual labor necessary.

Further and more limited objects of the invention will appear-as the description proceeds and by reference to the accompanying drawings in which Fig. 1 is a view in side elevation illustrating the'preferred. embodiment of my invention; Fig. 2 is a view in front elevation of the apparatus disclosed in Fig. 1; Fig. 3 is a view similar toFig. 2 with'the parts in a different position; Fig. 4 is a view partly in vertical section'and partly in front elevation disclosing the means for ejecting or extruding the refractory material into the mold; Fig. 5 is a horizontal sectional view on the line 5-5 of Fig. 4; Fig. 6 is a fragmentary vertical sectional view illustrating the mold and the means for positioning the form or core therein; Fig. 7 is a view partly in vertical section and partly in elevation illustrating the mechanism for lifting the mold; Fig. 8 is a horizontal sectional view on the line 8--8 of Fig.1 Fig. 9 is a fragmentary sectional view illustrating a slightly modified form of apparatus for forming a heat- I ing unit having a hollow form or core; Fig. 10 is a fragmentary sectional view illustrating a slightly modified form of apparatus for forming a heat ing unit having a solid form or core; Fig. 11 is a electrical resistance heating units by extruding no the refractory insulating material around and about the resistor.

Referring'now to the drawings, the apparatus.

consists essentially of a press having a base portion 1 and a top or head portion 2; Secured to the base portion 1 and extending upwardly therefrom is a tubular member or sleeve 3 in which are provided vertically extending slots 4 and 5. Slidably arranged within the sleeve 3 is an interiorly threaded sleeve 3*. Threadedly secured within the upper portion of the inner sleeve 3 is a pin 6 having a reduced upper end '7 over which fits a base block 8. J ournaled in the lower end' of the sleeve 3 and projecting outwardly on opposite sides thereof is a pin 9 which is journaled in bearings l0 and 11. Non-rotatably secured on the opposite ends of the pin. 9 and exteriorly of the sleeve 3 are a pair of collars or sleeves 12 and 13 to which are rigidly secured a pair of upwardly extending links 14 and 15 to the upper ends of which are pivotally connected a pair of links 16 and 1'7. The upper" ends of the links 16 and 17 are connected with the inner sleeve 3 by means of bolts 18 and 19 and bushings 18 and 19 Rigidly connecting the opposite'ends of the links 14 and 15 is a yoke 20 which extends around the sleeve 3 as shown most clearly in Figs. 1, 2 and 3 and to which is rigidly connected an operating lever 21 having a handle 22. By operating the handle 21 the sleeve 3 may be raised and lowered within the sleeve 3. The links 14, 15 and 16, 17 are arranged to produce a toggle action which looks the sleeve in the raised position when the parts are moved to the position shown in Fig. 3.

The base blocks is'preferably annular in shape and provided with an overhanging peripheral portion having openings therein. Secured over thebase block 8 is an annular ring 23 which is preferably formed of rubber, or some like material. Resting on the annular ring 23 is a collet 24 which is secured to block 8 by bolts 25. The collet 24 is'preferably annular in shape and provided with a central depression adapted to receive therein a mold 26 which also has a circular depression therein. The mold 26 is provided with bolts 33 and 34 and suitable nuts and washers 35,

36 and 37, 38. The cylinder 31is adapted to contain a. mass of extrudible insulation forming material and is adapted to be pivoted about the bolt 33, to the position shown in dotted lines in Fig.- 1 whereby to permit filling of the same. Fitting .within the cylinder 31 is a piston 39 from which extends a piston rod 40 which extends through an opening in the overhanging portion of the head 2. The upper end of the piston rod 40 terminates in a rack 41. Pivotally mounted on the head of the press is an operating lever 42 to one end of which is secured a weight 43 and to the opposite end of which is secured a handle 44. This operating lever includes a gear which engages the rack 41 and operates the piston 39.

By pulling downwardly on the handle 44, -the piston may be forced into the cylinder 31.

The interior of the cylinder 31 tapers inwardly at its lower end, as shown most clearly in Fig. 4 andterminates in an opening 46. Positioned over the opening 46 is a die 47 having a plurality of openings 48 therein. The die 47 is provided with a circular shoulder which fitsinto an ,annu- 1 lar r'eces's provided about the opening 46. Disposed below the die-47 is a nozzle 49 which engages the lower face of the die 47 and is clamped against the lower end of the cylinder by means of bolts 50 and 51 which extendthrough an apertured clamping ring 52 having openings 53 and 54 therein. The openings 53 and 54 are considerably larger than bolts 50 and 51 and secured collar 57. Extending axially of the sleeve 57 is a bore .58 which connects with a groove 59 provided in the upper end of the sleeve. Extending radially of the die 47 is a bore 60 which communi cates with the bore 59, the purpose of which will hereinafter appear. The nozzle 49 and the sleeve 57 project downwardly between the extensions 28 and are disposed in axial alignment with the mold 26.

We will now describe the operation of the apparatus when used in insulating resistor. elements of the cartridge or sheathed type. We first provide a metal sheath 61 which has an overhanging peripheral portion 62 and an annular upstanding'portion 63. The sheath also is provided with a bolt 64 which is centrally positioned therein and is threaded at its upper end. Secured over the, bolt 64 is a form or core 65 formed of suitable material and on which is Wound a resistor 66 which is partially embedded in grooves provided in the core, as shown-most clearly in Fig. 6. We place over-the form or core 65 a guide block 67 having a pair of parallel bores therein through which the upper ends of the resistor 66 project. After the form or core has been placed within the sheath, the sheath is placed within the mold 24 which has a.- suitably formed depression therein to receive the same. The parts then occupy the position shown in Fig. 2. The handle 22 is .then operated to raise the'mold 24 to the position shown inFig. 3 whereupon the nozzle 49 engages over the upper ends of the sheath and.

the sleeve 57 engages over the guide block 67 as shown in Fig. 6. The handle 44 is then depressed to actuate the piston to extrude the insulation forming material through the bores 48 opening in the die '47 and thence downwardly about the sleeve 5'7 and nozzle 49 into the sheath. The material is extruded into the sheath about and around the resistor until the sheath is filled. The

extruded material will pass down'and over the resistor and fill the space between the resistor and the side' wallsof the cartridge or. sheath.

When this space has been substantially filled, the resistance and pressure being continued, hydrostatic pressure will develop within the cartridge static pressure will increase and the mobile ma 'and force the mobile material about and around means of a handle 22 and the shell or cartridge removed.

In Fig. 9 there is disclosed a slightly modified form of our invention which is adapted for forming sheathed heating units having a hollow form or core. In this form'of invention the mold 26 is replaced by a mold 26 The guide block 67 is also replaced by a guide block 67 which has a central projection 6'7 thereon which cooperates with a projection 61 in the bottom of the sheath 61 to center the form or core within the mold.

In Fig. 10 we have disclosed another slightly modified form of apparatus which is especially adapted for forming unsheathed heating units j having a solid form or core. In this form of the apparatus, the mold 26 is removed and replaced by mold 26 having an annular upstanding portion 26 adapted to engage in the annular recess in the nozzle 49. The guide block 67 is also replaced by a guide block 67 having a projection 67 thereon. Arranged within the lower end of. the mold is a piston 68 having a central projection 69 thereon which cooperates with the projection 67 to center the'form or core within the mold. The piston also has a stem or projection 70 thereon which projects through an opening in the lower end of the mold and serves to facilitate the removal of the finished article.

In the specification andclaims we have used the expressions insulating material or insulation forming material". By these expressions we mean to include any material which is already an electrical insulator when extruded about the resistor, such as zirconium silicate, aluminum oxide or magnesium oxide in comminuted or pulverulent form admixed with a substance for contributing mobility; or a material such as metallic magnesium preferably in comminuted or powdered form for facilitating extrusion, and subsequent treatment for changing it into a material having electrical insulating properties such as referred to in a copending application of Edwin L. Wiegand, Serial No. 428665, filed February 15 In certain of the claims the term mold is used in its broad sense to include any kind of .receptacle which may or may not form a part of the finished heating element.

It will now be clear that we have provided an apparatus which will accomplish the objects of the invention as hereinbefore stated. Various changes may be made in the details of construction and arrangement of parts without departing from the spirit of our invention. For example, the nozzle 49 and sleeve 5'7 may be modified so as to be suitable for'insulating different shaped resistor elements which maybe either sheathed or unsheathed. The detailsofithe specific apparatus for operating the piston and for lifting the mold may also be modified if desired. The embodiment of the invention herein disclosed is. therefore merely illustrative and is not to be considered in a limiting sense, as the invention is limited only in accordance with the scope of the appended claims.

Having thus described our invention, what we claim is:

1. An' apparatus for insulating electrical resistors comprising a mold adapted to receive a form having a resistor positioned thereon, means forextruding insulating material and cooperating means disposed between said mold and extrusion device for conducting insulating material into said mold for venting the same.

2. An apparatus for insulating electrical resistors comprising a base member, a mold adapted to receive therein a form having a resistor positioning means thereon, a container adapted to contain a mass of insulation forming material, and means for forcing said material therefrom into said mold, said container having a nozzle thereon adapted to engage with said mold, means detachably securing said nozzle in place and means venting the said mold through said nozzle. i

3. An apparatus for insulating electrical resistors comprising a base member, a mold adapted to receive therein a form having rematerial, means for forcing said material therefrom into said mold, said container having a nozzle thereon adapted for connection with said mold, said nozzle including means for closing said mold and means for venting the mold to the atmosphere through the nozzle during the filling operation.

4. An apparatus for insulating electrical resistors comprising amold adapted to receive thereon a sheath containing a resistor, and means for extruding into said sheath and about said resistor a mass of insulating material, said means including a nozzle and means for venting said sheath through said nozzle during the filling operation.

5. An apparatus for insulating electrical resistors comprising a mold adapted to receive therein a sheath having a resistor affixed there-,

in in diverse planes, means for filling said sheath by extruding thereinto and about said resistor a quantity of insulating material, said means 'including a container adapted to contain a quantity of the insulating material, and a nozzle havingone end connected withsaid container and its opposite end adapted for connection with said sheath whereby the refractory material may be forced into said sheath, and means venting said sheath through said nozzle.

6. An apparatus for insulating electrical resistors comprising amold adapted to receive therein a sheath having a core positioned therein and on which a resistor is afilxed in diverse planes, means for filling said sheath by extruding thereinto and about said resistor a quantity of insulating material, said means including a plunger, 9, container adapted to contain a quantity of insulation forming material and adjustably mounted so as to be moved into alignment with said plunger, a nozzle having one end connected with said container and an orifice adapted for connection with saidsheath whereby the material may be forced-into said sheath, said nozzle including means for engaging said sheath and holding the same in place, and, means for venting said sheath to the atmosphere through said nozzle during the filling operation.

7. An apparatus f r forming electrical resistor heating elements comprising a mold adapted to receive and support a resistor therein, means for extruding insulating material into said mold and about a resistor positioned therein, said means including a nozzle adapted to engage and close said mold, a member carried by said nozzle and adapted to receive the projecting ends of said resistor, and means for venting said mold through said nozzle during the filling operation. i

9. An apparatus for insulating electrical resistors comprising a base member, a mold. adapted to receive therein a form having a resistor positioned thereon, a container adapted. to contain'a mass of insulation forming material, means for forcing said material therefrom into said mold, said container having a nozzle thereon adapted for connection with said mold, means w adjustably securing said container in place whereby to permit filling thereof without removal, said nozzle depending from said container and adapted to engage and position said form, and means for venting said mold through said nozzle.

EDWIN L. WIEGAND.

ALBERT P. WIEGAND. 

